scholarly journals Shear Melting and High Temperature Embrittlement: Theory and Application to Machining Titanium

MRS Advances ◽  
2016 ◽  
Vol 1 (35) ◽  
pp. 2477-2482
Author(s):  
Graeme J Ackland ◽  
Con Healy ◽  
Sascha Koch ◽  
Florian Brunke ◽  
Carsten Siemers
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
High Temperature ◽  
Melting Point ◽  
Shear Band ◽  
Titanium Alloys ◽  
Rare Earth Metals ◽  
Shear Bands ◽  
Alloy Matrix ◽  
Dislocation Mechanism

ABSTRACTWe show that alloying with rare earth metals (REMs) can dramatically improve the machineability of a range of titanium alloys, even though the REM is not incorporated in the alloy matrix. The mechanism for this is that under cutting, shear bands are formed within which the nano-precipitates of REM are shear mixed. This lowers the melting point such that the mechanism of deformation changes from dislocation mechanism to localised amorphisation and shear softening. The material then fractures along the thin, amorphous shear-band. Outside the shear band, the REM remains as precipitates. The new alloys have similar mechanical properties and biocompatibility to conventional materials.

Effect of Rare Earth Er on the Microstructure and Mechanical Properties of High Temperature Titanium Alloys

2017 ◽  
Vol 898 ◽  
pp. 586-591
Author(s):  
Bo Long Li ◽  
Tong Bo Wang ◽  
Peng Han ◽  
Zhen Qiang Wang ◽  
Zuo Ren Nie
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
High Temperature ◽  
Titanium Alloys ◽  
Aging Treatment ◽  
Thermal Exposure ◽  
Second Phase ◽  
Creep Properties ◽  
Cast Alloys ◽  
Mean Size

The microstructures and mechanical properties of the high temperature titanium alloys containing Er, i.e. Ti-6Al-2.5Sn-4Zr-0.3Mo-1Nb-0.35Si-xEr (x=0, 0.1, 0.3wt%), were investigated. Both the grain size and lamellar structure inside grains were significantly refined with the addition of Er in as-cast alloys. Lamellar and duplex microstructures were obtained after forging and heat treatment. Silicide precipitates were generated in the boundary of lamellar α phase after aging treatment. Meanwhile, a few α2 phase were precipitated in the alloys after aging treatment. After 600°C /100h thermal exposure, the α2 phases with a mean size of 7nm and spacing of 10 nm were precipitated homogeneously in α lamellar. The creep properties were significantly improved by the addition of rare earth Er due to the formation of the second phase containing Er, silicide and α2 phase.

Effect of Rare Earth on High Temperature Properties of Heat-Resisting Steel

2012 ◽  
Vol 557-559 ◽  
pp. 108-111
Author(s):  
Xiao Liu ◽  
Hu Fei Zhang
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Rare Earth ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Cleavage Fracture ◽  
Oxidation Rate ◽  
High Temperature Mechanical Properties ◽  
Dimple Fracture ◽  
Reduction Of Area

The oxidation resistance and high temperature mechanical properties of FeCrNi heat-resisting steel are analyzed and studied. The results show that the oxidation resistance of the heat-resisting steel is improved remarkably after adding RE. The value of oxidation rate of Sample 1 (without adding RE) is 1.71 times higher than Sample 2, respectively at 1423K. And the value of oxidation rate of Sample 1 is 1.4 times higher than Sample 2, respectively at 1473K. The fracture mode of heat-resisting stainless steel is typical cleavage fracture, but dimple fracture after adding RE into the steel. The high temperature mechanical properties of heat-resisting steel is improved obviously by RE. In comparison with heat-resisting stainless steel without RE, the reduction of area of heat-resisting stainless steel with RE is increased 26.27% at 1123K.

Effect of CeCl3-Containing Flux on Microstructure and Mechanical Properties of Mg Alloy Containing Rare Earth

2007 ◽  
Vol 546-549 ◽  
pp. 563-566
Author(s):  
Wen Jiang Ding ◽  
Guo Hua Wu ◽  
Bong Sun You ◽  
Dong Yim Chang
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
High Temperature ◽  
Magnesium Alloy ◽  
Loss Rate ◽  
Alloy Element ◽  
Corrosion Properties ◽  
High Temperature Mechanical Properties ◽  
Β Phase ◽  
Element Loss

The effects of CeCl3-containing fluxes on RE element loss, the high temperature mechanical properties, microstructure and corrosion properties of magnesium alloy containing RE have been studied. The results showed that a certain amount of CeCl3 in purification fluxes restrained the reaction between the Ce element and fluxes to decrease the loss of Ce in alloys. With the flux containing 9% CeCl3, the loss rate of alloy element Ce can be reduced from 26.9% to 3.4%, and the σb and δ of the alloys at 150°C counld be improved from 160.9MPa and 6.2% to 176.5MPa and 7.9% compared with that of conventional MgCl2-containing flux , respectively. Besides, the coarse β phase and rod-like RE phase were refined effectively by CeCl3-containing fluxes.

scholarly journals An experimental research on the machinability of a high temperature titanium alloy BTi-6431S in turning process

2018 ◽  
Vol 5 ◽  
pp. 12
Author(s):  
Yanfeng Gao ◽  
Yongbo Wu ◽  
Jianhua Xiao ◽  
Dong Lu
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Tool Wear ◽  
Titanium Alloys ◽  
Cutting Forces ◽  
Shear Bands ◽  
Cutting Parameters ◽  
Aircraft Manufacturing ◽  
Mechanical And Physical Properties ◽  
Alpha Titanium

Titanium alloys are extensively applied in the aircraft manufacturing due to their excellent mechanical and physical properties. At present, the α + β alloy Ti6Al4V is the most commonly used titanium alloy in the industry. However, the highest temperature that it can be used only up to 300 °C. BTi-6431S is one of the latest developed high temperature titanium alloys, which belongs to the near-α alloy group and has considerably high tensile strength at 650 °C. This paper investigates the machinability of BTi-6431S in the terms of cutting forces, chip formation and tool wear. The experiments are carried out in a range of cutting parameters and the results had been investigated and analyzed. The investigation shows that: (1) the specific cutting forces in the machining of BTi-6431S alloy are higher than in the machining of Ti6Al4V alloy; (2) the regular saw-tooth chips more easily formed and the shear bands are narrower in the machining of BTi-6431S; (3) SEM and EDS observations of the worn tools indicate that more cobalt elements diffuse into the workpiece from tool inserts during machining of BTi-6431S alloy, which significantly aggravates tool wear rate. The experimental results indicate that the machinability of BTi-6431S near alpha titanium alloy is significantly lower than Ti-6Al-4V alloy.

Effect of Transition Metal Silicides on Microstructure and Mechanical Properties of Ultra-High Temperature Ceramics

2013 ◽  
pp. 125-179 ◽  
Author(s):  
Laura Silvestroni ◽  
Diletta Sciti
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Melting Point ◽  
Leading Edge ◽  
High Melting ◽  
High Melting Point ◽  
Ultra High Temperature Ceramics ◽  
Sintering Additives ◽  
Self Diffusion ◽  
Ultra High Temperature

The IV and V group transition metals borides, carbides, and nitrides are widely known as ultra-high temperature ceramics (UHTCs), owing to their high melting point above 2500°C. These ceramics possess outstanding physical and engineering properties, such as high hardness and strength, low electrical resistivity and good chemical inertness which make them suitable structural materials for applications under high heat fluxes. Potential applications include aerospace manufacturing; for example sharp leading edge parts on hypersonic atmospheric re-entry vehicles, rocket nozzles, and scramjet components, where operating temperatures can exceed 3000°C. The extremely high melting point and the low self-diffusion coefficient make these ceramics very difficult to sinter to full density: temperatures above 2000°C and the application of pressure are necessary conditions. However these processing parameters lead to coarse microstructures, with mean grain size of the order of 20 µm and trapped porosity, all features which prevent the achievement of the full potential of the thermo-mechanical properties of UHTCs. Several activities have been performed in order to decrease the severity of the processing conditions of UHTCs introducing sintering additives, such as metals, nitrides, carbides or silicides. In general the addition of such secondary phases does decrease the sintering temperature, but some additives have some drawbacks, especially during use at high temperature, owing to their softening and the following loss of integrity of the material. In this chapter, composites based on borides and carbides of Zr, Hf and Ta were produced with addition of MoSi2 or TaSi2. These silicides were selected as sintering aids owing to their high melting point (>2100°C), their ductility above 1000°C and their capability to increase the oxidation resistance. The microstructure of fully dense hot pressed UHTCs containing 15 vol% of MoSi2 or TaSi2, was characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on microstructural features detected by TEM, thermodynamical calculations, and the available phase diagrams, a densification mechanism for these composites is proposed. The mechanical properties, namely hardness, fracture toughness, Young’s modulus and flexural strength at room and high temperature, were measured and compared to the properties of other ultra-high temperature ceramics produced with other sintering additives. Further, the microstructural findings were used to furnish possible explanations for the excellent high temperature performances of these composites.

Effect of Rare Earth Metals on the Mechanical Properties and Fractography of Al–Si-Based Alloys

2019 ◽  
Vol 14 (1) ◽  
pp. 108-124 ◽  
Author(s):  
M. F. Ibrahim ◽  
M. H. Abdelaziz ◽  
A. M. Samuel ◽  
H. W. Doty ◽  
F. H. Samuel
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
Rare Earth Metals

scholarly journals The Influence Of The Rare Earth Metals Modification On The Fracture Toughness Of G17CrMo5-5 Cast Steel At Low Temperatures

2015 ◽  
Vol 60 (2) ◽  
pp. 773-777 ◽  
Author(s):  
I. Dzioba ◽  
J. Kasińska ◽  
R. Pała
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Rare Earth ◽  
Low Temperatures ◽  
Cast Steel ◽  
Rare Earth Metals ◽  
Positive Influence ◽  
Reference Temperature ◽  
Brittle To Ductile Transition ◽  
The Rare Earth

Abstract This paper presents the influence of the rare earth metals (REM) modification on mechanical properties and fracture toughness of G17CrMo5-5 cast steel at low temperatures. The REM was in the form of mishmetal. The research has been performed on serial (several) industrial melts. The fracture toughness values of unmodified and modified cast steel at the temperature range from −80°C to 20°C were tested. The reference temperatures of the brittle-to-ductile transition, TQ, for both unmodified and modified cast steel were determined. The positive influence of the modification by REM on the fracture toughness and the reference temperature TQ are shown.

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